Adipose tissue-liver axis in alcoholic liver disease

An Update on Animal Models of Alcohol-Associated Liver Disease

Alcohol-associated liver disease (ALD) is a significant global health concern and a leading cause of liver disease-related deaths. However, the treatment options are limited due to the lack of animal models that accurately replicate ALD pathogenesis. An ideal ALD animal model should have pathological characteristics similar to those of human ALD, with a clear pathological process and ease of drug intervention. Over the years, researchers have focused on developing ideal ALD preclinical animal models by testing various methods, such as ad libitum drinking water with ethanol, acute, single large doses of ethanol gavage, multiple alcohol gavages in a short period, the Lieber-DeCarli liquid diet feeding model, the intragastric infusion model, and the Gao-binge model. With the increasing occurrence of obesity and metabolic dysfunction-associated steatotic liver disease, a new category of metabolic and alcohol-associated liver disease (MetALD) is also emerging. Studies have investigated the combined effects of a high-fat diet combined with binge alcohol or drinking water containing ethanol to mimic MetALD. In addition to mice, other species such as rats, guinea pigs, zebrafish, and non-human primates have also been tested to establish ALD preclinical models. This review aims to summarize current animal ALD models, particularly the emerging MetALD models, with the hope of providing a valuable reference for establishing more effective animal models in ALD studies in the future.

Immunology and treatments of fatty liver disease

Alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD) are two major chronic liver diseases worldwide. The triggers for fatty liver can be derived from external sources such as adipose tissue, the gut, personal diet, and genetics, or internal sources, including immune cell responses, lipotoxicity, hepatocyte death, mitochondrial dysfunction, and extracellular vesicles. However, their pathogenesis varies to some extent. This review summarizes various immune mechanisms and therapeutic targets associated with these two types of fatty liver disease. It describes the gut-liver axis and adipose tissue-liver crosstalk, as well as the roles of different immune cells (both innate and adaptive immune cells) in fatty liver disease. Additionally, mitochondrial dysfunction, extracellular vesicles, microRNAs (miRNAs), and gastrointestinal hormones are also related to the pathogenesis of fatty liver. Understanding the pathogenesis of fatty liver and corresponding therapeutic strategies provides a new perspective for developing novel treatments for fatty liver disease.

PRDM16 in thermogenic adipocytes mediates an inter-organ protective signaling against alcohol-associated liver disease

Alcohol-associated liver disease (ALD) is one of the major chronic liver diseases and despite the dire clinical needs and extensive research efforts, no effective therapies are available for late-stages of ALD except for liver transplantation. Adipose tissue dysfunction has been implicated in the progression of ALD. Furthermore, it has been previously suggested that thermogenic fat can be activated after alcohol consumption. In this study, increased thermogenic gene expression was detected in both classical brown adipose tissue and beige adipocytes in mice that were given alcohol challenges even when housed at thermoneutrality. In particular, higher expression level of Prdm16, the key transcriptional co-component for beige fat function, was observed in the subcutaneous fat of mice after alcohol challenges. The objective of the present study is to explore the functional significance of adipocyte PRDM16 in the context of ALD. Even though Prdm16 adipocyte-specific-deleted mice (Prdm16-adKO) did not show liver defects at the basal level, following two different alcohol challenge regimens, exacerbated ALD phenotypes were observed in Prdm16-adKO mice compared to that of the control Prdm16 fl/fl mice. Mechanistic investigation suggests that adipose dysfunction after alcohol abuse, including alcohol-induced changes in adipose lipolytic activity, fatty acid oxidation and adipokine levels, may render the worsened ALD phenotype in Prdm16-adKO mice. These results indicate PRDM16-mediated signaling in fat plays a protective role against liver injury caused by alcohol abuse, suggesting it may represent a potential therapeutic target against ALD.

Hepatoprotective effects of fruits pulp, seed, and peel against chemical-induced toxicity: Insights from in vivo studies

The liver is a vital organ in human physiology positioned in the upper right quadrant of the peritoneal cavity, which plats a critical role in metabolic processes, detoxification of various substances and overall homeostasis. Along with these critical functions, hepatic diseases impose as significant global health threat. Liver illness is the cause of two million fatalities every year, or 4% of all deaths. Traditionally, healthcare providers have prescribed antibacterial and antiviral medications to address liver illness. Nephrotoxicity is a frequently observed negative reaction to drugs, with the majority of such events happening in individuals who have advanced cirrhosis. Thus, recognizing this gap, there is a dire need of exploration of pharmaceutical alterative for hepatic diseases, with special focus on their efficacy and reduced toxicity. Fruits have long been known to therapeutic impact on human health, thus exploration of fruits components namely pulp, seeds and peels containing phytochemicals have emerged as a promising avenue for hepatoprotective interventions. Thus, review comprehends the information about worldwide burden of chemical induced toxicity and injuries as well as highlight the on-going challenges in hepatic disease management. It also shed light on the valuable contributions fruit parts and their phytocompounds obtained from different components of fruits. Fruit pulp, especially when rich in flavonoids, has demonstrated significant potential in animal model studies. It has been observed to enhance the activity of antioxidant enzymes and reduce the expression of pro-inflammatory markers. The methanolic and ethanolic extracts have demonstrated the most favorable outcomes. Further, this review also discusses about the safety assessments of fruits extracts for their utilization as hepatoprotective agents.

Penthorum chinense Pursh extract ameliorates alcohol-related fatty liver disease in mice via the SIRT1/AMPK signaling axis

Penthorum chinense Pursh (P. chinense), a functional food, has been applied to protect the liver against alcohol-related fatty liver disease (ALD) for a long history in China. This study was designed to evaluate the ameliorative activity of the polyphenolic fraction in P. chinense (PGF) depending on the relief of ALD. The ALD mouse model was established by exposing the mice to a Lieber-DeCarli alcohol liquid diet. We found that PGF administration significantly ameliorated alcohol-induced liver injury, steatosis, oxidative stress, and inflammation in mice. Furthermore, alcohol-increased levels of the critical hepatic lipid synthesis proteins sterol regulatory element binding transcription factor (SREBP-1) and diacylglycerol o-acyltransferase 2 (DGAT2) were attenuated by PGF. Similarly, PGF inhibited the expression of the lipid transport protein very low-density lipoprotein receptor (VLDLR). Interestingly, PGF restored alcohol-inhibited expression of carnitine palmitoyltransferase 1 (CPT1) and peroxisome proliferator-activated receptor alpha (PPARα), essential fatty acid β-oxidation proteins. Mechanistic studies revealed that PGF protects against alcohol-induced hepatocyte injury and lipid deposition via the SIRT1/AMPK signaling pathway. In sum, this research clearly demonstrated the protective effects of PGF against ALD, which was mediated by activating SIRT1/AMPK pathways in hepatocytes. We provide a new theoretical basis for using P. chinense as a functional food in ALD.

Pharmacological inhibition of the Src homology phosphatase 2 confers partial protection in a mouse model of alcohol-associated liver disease

Alcohol-associated liver disease (ALD) is a leading factor of liver-related death worldwide. ALD has various manifestations that include steatosis, hepatitis, and cirrhosis and is currently without approved pharmacotherapies. The Src homology phosphatase 2 (Shp2) is a drug target in some cancers due to its positive regulation of Ras-mitogen-activated protein kinase signaling and cell proliferation. Shp2 pharmacological inhibition yields beneficial outcomes in animal disease models, but its impact on ALD remains unexplored. This study aims to investigate the effects of Shp2 inhibition and its validity using a preclinical mouse model of ALD. We report that the administration of SHP099, a potent and selective allosteric inhibitor of Shp2, partially ameliorated ethanol-induced hepatic injury, inflammation, and steatosis in mice. Additionally, Shp2 inhibition was associated with reduced ethanol-evoked activation of extracellular signal-regulated kinase (ERK), oxidative, and endoplasmic reticulum (ER) stress in the liver. Besides the liver, excessive alcohol consumption induces multi-organ injury and dysfunction, including the intestine. Notably, Shp2 inhibition diminished ethanol-induced intestinal inflammation and permeability, abrogated the reduction in tight junction protein expression, and the activation of ERK and stress signaling in the ileum. Collectively, Shp2 pharmacological inhibition mitigates the deleterious effects of ethanol in the liver and intestine in a mouse model of ALD. Given the multifactorial aspects underlying ALD pathogenesis, additional studies are needed to decipher the utility of Shp2 inhibition alone or as a component in a multitherapeutic regimen to combat this deadly malady.

Hepatic TRPC3 loss contributes to chronic alcohol consumption-induced hepatic steatosis and liver injury in mice

Emerging evidence discloses the involvement of calcium channel protein in the pathological process of liver diseases. Transient receptor potential cation channel subfamily C member 3 (TRPC3), a ubiquitously expressed non-selective cation channel protein, controls proliferation, inflammation, and immune response via operating calcium influx in various organs. However, our understanding on the biofunction of hepatic TRPC3 is still limited. The present study aims to clarify the role and potential mechanism(s) of TRPC3 in alcohol-associated liver disease (ALD). We recently found that TRPC3 expression plays an important role in the disease process of ALD. Alcohol exposure led to a significant reduction of hepatic TRPC3 in patients with alcohol-related hepatitis (AH) and ALD models. Antioxidants (N-acetylcysteine and mitoquinone) intervention improved alcohol-induced suppression of TRPC3 via a miR-339-5p-involved mechanism. TRPC3 loss robustly aggravated the alcohol-induced hepatic steatosis and liver injury in mouse liver; this was associated with the suppression of Ca2+/calmodulin-dependent protein kinase kinase 2 (CAMKK2)/AMP-activated protein kinase (AMPK) and dysregulation of genes related to lipid metabolism. TRPC3 loss also enhanced hepatic inflammation and early fibrosis-like change in mice. Replenishing hepatic TRPC3 effectively reversed chronic alcohol-induced detrimental alterations in ALD mice. Briefly, chronic alcohol exposure-induced TRPC3 reduction contributes to the pathological development of ALD via suppression of the CAMKK2/AMPK pathway. Oxidative stress-stimulated miR-339-5p upregulation contributes to alcohol-reduced TRPC3. TRPC3 is the requisite and a potential target to defend alcohol consumption-caused ALD.

Adipose lipolysis is important for ethanol to induce fatty liver in the National Institute on Alcohol Abuse and Alcoholism murine model of chronic and binge ethanol feeding

BACKGROUND AND AIMS

Alcohol-associated liver disease (ALD) pathologies include steatosis, inflammation, and injury, which may progress to fibrosis, cirrhosis, and cancer. The liver receives ~60% of fatty acids from adipose tissue triglyceride hydrolysis, but the role of this lipolytic pathway in ALD development has not been directly examined in any genetic animal models with selective inactivation of adipose lipolysis.

APPROACH AND RESULTS

Using adipose-specific comparative gene identification-58 (CGI-58) knockout (FAT-KO) mice, a model of impaired adipose lipolysis, we show that mice deficient in adipose lipolysis are almost completely protected against ethanol-induced hepatic steatosis and lipid peroxidation when subjected to the National Institute on Alcohol Abuse and Alcoholism chronic and binge ethanol feeding model. This is unlikely due to reduced lipid synthesis because this regimen of ethanol feeding down-regulated hepatic expression of lipogenic genes similarly in both genotypes. In the pair-fed group, FAT-KO relative to control mice displayed increased hepatocyte injury, neutrophil infiltration, and activation of the transcription factor signal transducer and activator of transcription 3 (STAT3) in the liver; and none of these were exacerbated by ethanol feeding. Activation of STAT3 is associated with a marked increase in hepatic leptin receptor mRNA expression and adipose inflammatory cell infiltration.

CONCLUSIONS

Our findings establish a critical role of adipose lipolysis in driving hepatic steatosis and oxidative stress during ALD development.

Gut microbiome as a therapeutic target for liver diseases

The prominent role of gut in regulating the physiology of different organs in a human body is increasingly acknowledged, to which the bidirectional communication between gut and liver is no exception. Liver health is modulated via different key components of gut-liver axis. The gut-derived products mainly generated from dietary components, microbial metabolites, toxins, or other antigens are sensed and transported to the liver through portal vein to which liver responds by secreting bile acids and antibodies. Therefore, maintaining a healthy gut microbiome can promote homeostasis of this gut-liver axis by regulating the intestinal barrier function and reducing the antigenic molecules. Conversely, liver secretions also regulate the gut microbiome composition. Disturbed homeostasis allows luminal antigens to reach liver leading to impaired liver functioning and instigating liver disorders. The perturbations in gut microbiome, permeability, and bile acid pool have been associated with several liver disorders, although precise mechanisms remain largely unresolved. Herein, we discuss functional fingerprints of a healthy gut-liver axis while contemplating mechanistic understanding of pathophysiology of liver diseases and plausible role of gut dysbiosis in different diseased states of liver. Further, novel therapeutic approaches to prevent the severity of liver disorders are discussed in this review.

Mitochondrial depolarization after acute ethanol treatment drives mitophagy in living mice

Ethanol increases hepatic mitophagy driven by unknown mechanisms. Type 1 mitophagy sequesters polarized mitochondria for nutrient recovery and cytoplasmic remodeling. In Type 2, mitochondrial depolarization (mtDepo) initiates mitophagy to remove the damaged organelles. Previously, we showed that acute ethanol administration produces reversible hepatic mtDepo. Here, we tested the hypothesis that ethanol-induced mtDepo initiates Type 2 mitophagy. GFP-LC3 transgenic mice were gavaged with ethanol (2-6 g/kg) with and without pre-treatment with agents that decrease or increase mtDepo-Alda-1, tacrolimus, or disulfiram. Without ethanol, virtually all hepatocytes contained polarized mitochondria with infrequent autophagic GFP-LC3 puncta visualized by intravital microscopy. At ~4 h after ethanol treatment, mtDepo occurred in an all-or-none fashion within individual hepatocytes, which increased dose dependently. GFP-LC3 puncta increased in parallel, predominantly in hepatocytes with mtDepo. Mitochondrial PINK1 and PRKN/parkin also increased. After covalent labeling of mitochondria with MitoTracker Red (MTR), GFP-LC3 puncta encircled MTR-labeled mitochondria after ethanol treatment, directly demonstrating mitophagy. GFP-LC3 puncta did not associate with fat droplets visualized with BODIPY558/568, indicating that increased autophagy was not due to lipophagy. Before ethanol administration, rhodamine-dextran (RhDex)-labeled lysosomes showed little association with GFP-LC3. After ethanol treatment, TFEB (transcription factor EB) translocated to nuclei, and lysosomal mass increased. Many GFP-LC3 puncta merged with RhDex-labeled lysosomes, showing autophagosomal processing into lysosomes. After ethanol treatment, disulfiram increased, whereas Alda-1 and tacrolimus decreased mtDepo, and mitophagy changed proportionately. In conclusion, mtDepo after acute ethanol treatment induces mitophagic sequestration and subsequent lysosomal processing.Abbreviations : AcAld, acetaldehyde; ADH, alcohol dehydrogenase; ALDH, aldehyde dehydrogenase; ALD, alcoholic liver disease; Alda-1, N-(1,3-benzodioxol-5-ylmethyl)-2,6-dichlorobenzamide; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; GFP, green fluorescent protein; LAMP1, lysosomal-associated membrane protein 1; LMNB1, lamin B1; MAA, malondialdehyde-acetaldehyde adducts; MAP1LC3/LC3, microtubule-associated protein 1 light chain 3; MPT, mitochondrial permeability transition; mtDAMPS, mitochondrial damage-associated molecular patterns; mtDepo, mitochondrial depolarization; mtDNA, mitochondrial DNA; MTR, MitoTracker Red; PI, propidium iodide; PINK1, PTEN induced putative kinase 1; PRKN, parkin; RhDex, rhodamine dextran; TFEB, transcription factor EB; Tg, transgenic; TMRM, tetramethylrhodamine methylester; TOMM20, translocase of outer mitochondrial membrane 20; VDAC, voltage-dependent anion channel.

Elevated S-adenosylhomocysteine induces adipocyte dysfunction to promote alcohol-associated liver steatosis

It has been previously shown that chronic ethanol administration-induced increase in adipose tissue lipolysis and reduction in the secretion of protective adipokines collectively contribute to alcohol-associated liver disease (ALD) pathogenesis. Further studies have revealed that increased adipose S-adenosylhomocysteine (SAH) levels generate methylation defects that promote lipolysis. Here, we hypothesized that increased intracellular SAH alone causes additional related pathological changes in adipose tissue as seen with alcohol administration. To test this, we used 3-deazaadenosine (DZA), which selectively elevates intracellular SAH levels by blocking its hydrolysis. Fully differentiated 3T3-L1 adipocytes were treated in vitro for 48 h with DZA and analysed for lipolysis, adipokine release and differentiation status. DZA treatment enhanced adipocyte lipolysis, as judged by lower levels of intracellular triglycerides, reduced lipid droplet sizes and higher levels of glycerol and free fatty acids released into the culture medium. These findings coincided with activation of both adipose triglyceride lipase and hormone sensitive lipase. DZA treatment also significantly reduced adipocyte differentiation factors, impaired adiponectin and leptin secretion but increased release of pro-inflammatory cytokines, IL-6, TNF and MCP-1. Together, our results demonstrate that elevation of intracellular SAH alone by DZA treatment of 3T3-L1 adipocytes induces lipolysis and dysregulates adipokine secretion. Selective elevation of intracellular SAH by DZA treatment mimics ethanol's effects and induces adipose dysfunction. We conclude that alcohol-induced elevations in adipose SAH levels contribute to the pathogenesis and progression of ALD.

Beneficial Effects of Betaine: A Comprehensive Review

Medicinal herbs and many food ingredients possess favorable biological properties that contribute to their therapeutic activities. One such natural product is betaine, a stable, nontoxic natural substance that is present in animals, plants, and microorganisms. Betaine is also endogenously synthesized through the metabolism of choline or exogenously consumed through dietary intake. Betaine mainly functions as (i) an osmolyte and (ii) a methyl-group donor. This review describes the major physiological effects of betaine in whole-body health and its ability to protect against both liver- as well as non-liver-related diseases and conditions. Betaine's role in preventing/attenuating both alcohol-induced and metabolic-associated liver diseases has been well studied and is extensively reviewed here. Several studies show that betaine protects against the development of alcohol-induced hepatic steatosis, apoptosis, and accumulation of damaged proteins. Additionally, it can significantly prevent/attenuate progressive liver injury by preserving gut integrity and adipose function. The protective effects are primarily associated with the regulation of methionine metabolism through removing homocysteine and maintaining cellular SAM:SAH ratios. Similarly, betaine prevents metabolic-associated fatty liver disease and its progression. In addition, betaine has a neuroprotective role, preserves myocardial function, and prevents pancreatic steatosis. Betaine also attenuates oxidant stress, endoplasmic reticulum stress, inflammation, and cancer development. To conclude, betaine exerts significant therapeutic and biological effects that are potentially beneficial for alleviating a diverse number of human diseases and conditions.

Alcohol-Related Liver Disease: Basic Mechanisms and Clinical Perspectives

Alcohol-related liver disease (ALD) refers to the liver damage occurring due to excessive alcohol consumption and involves a broad spectrum of diseases that includes liver steatosis, steatohepatitis, hepatitis, cirrhosis, and hepatocellular carcinoma (HCC). The progression of ALD is mainly associated with the amount and duration of alcohol usage; however, it is also influenced by genetic, epigenetic, and environmental factors. The definite diagnosis of ALD is based on a liver biopsy, although several non-invasive diagnostic tools and serum biomarkers have emerging roles in the early detection of ALD. While alcohol abstinence and nutritional support remain the cornerstone of ALD treatment, growing evidence has revealed that the therapeutic agents that target oxidative stress or gut-liver axis, inflammatory response inhibition, and liver regeneration enhancement also play a role in ALD management. Furthermore, microRNAs modulation and mesenchymal stem cell-based therapy have emerging potential as ALD therapeutic options. This review summarizes the updated understanding of the pathophysiology, diagnosis, and novel therapeutic approaches for ALD.

Curative effects of the aqueous extract of Tithonia diversifolia (Hemsl.) A. gray (Asteraceae) against ethanol induced-hepatotoxicity in rats

OBJECTIVES

Tithonia diversifolia (Asteraceae) is used in Cameroonian traditional medicine for the treatment of several diseases amongst which are hepatic disorders. Anti-inflammatory, analgesic and anti-diabetic properties have been reported but, there is no scientific information on its hepato-protective effects. The aim of this study was to evaluate the curative effects of the Tithonia diversifolia (T. diversifolia) leaves aqueous extract on ethanol induced-hepatotoxicity in rats.

METHODS

Ethanol 40° (4 g/kg) was administered daily by intragastric gavage for 21 days, and then the extract was administered concomitantly with ethanol for two more weeks. Some biochemical serum and tissue parameters were evaluated. Histopathologic analysis of the liver was carried out.

RESULTS

The ingestion of ethanol induced a significant reduction of body weight and a significant increase in some markers of hepatic function (Alanine Amino-transferase, Aspartate Amino-transferase, alkaline phosphatase, gamma glutamyl-transferase, total bilirubin and albumin). These alterations were accompanied by a significant increase in the levels of serum triglycerides (p<0.001). Intoxicated animals were also characterized by a significant decrease of reduced glutathione and nitrites concentrations, catalase and superoxide dismutase activities as well as an increase of malondialdehyde levels. The histopathological examination showed vascular congestion, disorganized parenchyma, liver inflammation and dilation of sinusoid. The extract at the doses of 60 and 120 mg/kg reversed ethanol-induced adverse effects.

CONCLUSION

Our study found that, the aqueous extract of T. diversifolia leaves has hepato-protective activity against ethanol-induced liver damages due partly to its antioxidant effect. This result justifies its empirical use for the treatment of liver problems.

Ethanol Disrupts Hormone-Induced Calcium Signaling in Liver

Receptor-coupled phospholipase C (PLC) is an important target for the actions of ethanol. In the ex vivo perfused rat liver, concentrations of ethanol >100 mM were required to induce a rise in cytosolic calcium (Ca²⁺) suggesting that these responses may only occur after binge ethanol consumption. Conversely, pharmacologically achievable concentrations of ethanol (≤30 mM) decreased the frequency and magnitude of hormone-stimulated cytosolic and nuclear Ca²⁺ oscillations and the parallel translocation of protein kinase C-β to the membrane. Ethanol also inhibited gap junction communication resulting in the loss of coordinated and spatially organized intercellular Ca²⁺ waves in hepatic lobules. Increasing the hormone concentration overcame the effects of ethanol on the frequency of Ca²⁺ oscillations and amplitude of the individual Ca²⁺ transients; however, the Ca²⁺ responses in the intact liver remained disorganized at the intercellular level, suggesting that gap junctions were still inhibited. Pretreating hepatocytes with an alcohol dehydrogenase inhibitor suppressed the effects of ethanol on hormone-induced Ca²⁺ increases, whereas inhibiting aldehyde dehydrogenase potentiated the inhibitory actions of ethanol, suggesting that acetaldehyde is the underlying mediator. Acute ethanol intoxication inhibited the rate of rise and the magnitude of hormone-stimulated production of inositol 1,4,5-trisphosphate (IP₃), but had no effect on the size of Ca²⁺ spikes induced by photolysis of caged IP₃. These findings suggest that ethanol inhibits PLC activity, but does not affect IP₃ receptor function. We propose that by suppressing hormone-stimulated PLC activity, ethanol interferes with the dynamic modulation of [IP₃] that is required to generate large, amplitude Ca²⁺ oscillations.

Homocysteine promotes hepatic steatosis by activating the adipocyte lipolysis in a HIF1α-ERO1α-dependent oxidative stress manner

Hyperhomocysteinemia (HHcy) is related to liver diseases, such as nonalcoholic fatty liver (NAFL). Although the precise pathogenesis of NAFL is still largely unknown, the links between organs seem to play a vital role. The current study aimed to explore the role of white adipose tissue in homocysteine (Hcy)-induced NAFL. Blood samples from nonhyperhomocysteinemia or hyperhomocysteinemia individuals were collected to assess correlation between Hcy and triglyceride (TG) or free fatty acids (FFAs) levels. C57BL/6 mice were maintained on a high-methionine diet or administered with Hcy (1.8 g/L) in the drinking water to establish an HHcy mouse model. We demonstrated that Hcy activated adipocyte lipolysis and that this change was accompanied by an increased release of FFAs and glycerol. Excessive FFAs were taken up by hepatocyte, which resulted in lipid accumulation in the liver. Treatment with acipimox (0.08 g kg ⁻¹ day ⁻¹), a potent chemical inhibitor of lipolysis, markedly decreased Hcy-induced NAFL. Mechanistically, hypoxia-inducible factor 1α (HIF1α)-endoplasmic reticulum oxidoreductin 1α (ERO1α) mediated pathway promoted H₂O₂ accumulation and induced endoplasmic reticulum (ER) overoxidation, ER stress and more closed ER-lipid droplet interactions, which were responsible for activating the lipolytic response. In conclusion, this study reveals that Hcy activates adipocyte lipolysis and suggests the potential utility of targeted ER redox homeostasis for treating Hcy-induced NAFL.

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Hcy elevates adipocyte lipolysis process.

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Inhibition of adipocyte lipolysis via acipimox improves the Hcy-induced nonalcoholic fatty liver.

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Adipocyte lipolytic response relies on ERO1α-mediated oxidative stress.

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Activation of adipocyte HIF1α mediates ERO1α upregulation.

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Deficiency of adipocyte HIF1α alleviates the Hcy-induced lipolytic response and nonalcoholic fatty liver.

New Insights into the Liver-Visceral Adipose Axis During Hepatic Resection and Liver Transplantation

In the last decade, adipose tissue has emerged as an endocrine organ with a key role in energy homeostasis. In addition, there is close crosstalk between the adipose tissue and the liver, since pro- and anti-inflammatory substances produced at the visceral adipose tissue level directly target the liver through the portal vein. During surgical procedures, including hepatic resection and liver transplantation, ischemia-reperfusion injury induces damage and regenerative failure. It has been suggested that adipose tissue is associated with both pathological or, on the contrary, with protective effects on damage and regenerative response after liver surgery. The present review aims to summarize the current knowledge on the crosstalk between the adipose tissue and the liver during liver surgery. Therapeutic strategies as well as the clinical and scientific controversies in this field are discussed. The different experimental models, such as lipectomy, to evaluate the role of adipose tissue in both steatotic and nonsteatotic livers undergoing surgery, are described. Such information may be useful for the establishment of protective strategies aimed at regulating the liver-visceral adipose tissue axis and improving the postoperative outcomes in clinical liver surgery.

Effects of Portulaca Oleracea Extract on Acute Alcoholic Liver Injury of Rats

The present study was envisaged to investigate the chemical constituents and the intervention effects of Portulaca oleracea extract (POE) on acute alcoholic liver injury of rats. The chemical composition of POE was detected by high performance liquid chromatography (HPLC). Sixty male Wistar rats were divided into 6 groups: Normal control (NC) group, acute alcoholic liver injury model group (ALI), low, medium and high dose of POE (25, 50, 100 mg/kg) groups and bifendate (BF, 3.75 mg/kg) group. Each group was given by intragastrical administration for 7 days. Alcoholic liver injury was induced in the experimental model by administering 50% ethanol at 8 mL/kg and repeated administration after 6 h, for a period of 7 days. The results showed that pretreatment with POE significantly reduced the ethanol-elevated serum level of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and triglyceride (TG). The activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) in liver were enhanced followed by administration of POE, while the content of nitric oxide (NO) and malondialdehyde (MDA) was found to decrease. Hepatic content of tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) was also reduced by POE treatment. These results indicated that POE could increase the antioxidant capacity and relieve the inflammatory injury of the liver cells induced by ethanol. Meanwhile, in our study, POE reduced the expression of miR-122, acetyl coenzyme A carboxylase (ACC) 1 mRNA and protein and increased the expression of lipoprotein lipase (LPL) mRNA and protein in liver, which indicated that POE could improve the lipid metabolism disorder induced by ethanol. Our findings suggested that POE had protective effects on acute alcoholic liver injury of rats.

Histologic analysis and lipid profiling reveal reproductive age-associated changes in peri-ovarian adipose tissue

BACKGROUND

Reproductive aging is a robust phenotype that occurs in all females and is characterized by a significant reduction in gamete quantity and quality, which can have negative consequences on both endocrine function and fertility. Age-associated differences in the oocyte, follicle, and ovary have been well-documented, but how the broader environment changes with age is less well understood. Fat is one of the largest organs in the body, and peri-gonadal adipose tissue surrounds the rodent ovary and comprises a local ovarian environment. The goal of this study was to characterize how peri-ovarian adipose tissue changes with advanced reproductive age.

METHODS

We isolated peri-gonadal adipose tissue from two cohorts of CB6F1 mice: reproductively young (6-12 weeks) and reproductively old (14-17 months). A comparative histological analysis was performed to evaluate adipocyte architecture. We then extracted lipids from the tissue and performed multiple reaction monitoring (MRM)-profiling, a mass spectrometry-based method of metabolite profiling, to compare the lipid profiles of peri-gonadal adipose tissue in these age cohorts.

RESULTS

We found that advanced reproductive age was associated with adipocyte hypertrophy and a corresponding decrease in the number of adipocytes per area. Of the 10 lipid classes examined, triacylglycerols (TAGs) had significantly different profiles between young and old cohorts, despite quantitative analysis revealing a decrease in the total amount of TAGs per weight of peri-gonadal adipose tissue with age.

CONCLUSIONS

These findings pinpoint age-associated physiological changes in peri-gonadal adipose tissue with respect to adipocyte morphology and lipid profiles and lay the foundation for future studies to examine how these alterations may influence both adipocyte and ovarian function.

Nutritional status in patients with liver cirrhosis

Aim of the study

To evaluate the nutritional status in patients with liver cirrhosis, depending on the stage of the disease. Fatty body mass, lean body mass and fluid content were determined, as well as basal metabolic rate.

Material and methods

The study included 56 patients with liver cirrhosis, aged 54 ±12 years. Nutritional status was determined with the BMI and albumin serum concentration. Fatty body mass, lean body mass and fluid content, as well as basal metabolic rate, were estimated by bioelectrical impedance, using a MALTRON 907 analyzer.

Results

Based on albumin concentration, malnutrition was diagnosed in over 80% of patients, usually (100%) in patients with liver cirrhosis belonging to Child-Pugh class C. In all patients, high energy demand was found in relation to basal metabolic rate. Average fatty body mass was comparable in all patients and ranged from 24 to 30%. Fluid content in the tissues was comparable in all evaluated groups and did not correlate with accompanying ascites. Fluid excess was found in 25% of Child-Pugh class A patients, in 59% of class B patients and in 60% of class C patients.

Conclusions

Malnutrition is present in over 80% of patients with liver cirrhosis, and its frequency correlates with the stage of liver insufficiency. Patients with liver cirrhosis show high energy demand for basal metabolic processes. Fluid excess is mainly found in patients with more severe liver injury, but it does not correlate directly with ascites.

Genetic and Epigenetic Modifiers of Alcoholic Liver Disease

Alcoholic liver disease (ALD), a disorder caused by excessive alcohol consumption is a global health issue. More than two billion people consume alcohol in the world and about 75 million are classified as having alcohol disorders. ALD embraces a wide spectrum of hepatic lesions including steatosis, alcoholic steatohepatitis (ASH), fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). ALD is a complex disease where environmental, genetic, and epigenetic factors contribute to its pathogenesis and progression. The severity of alcohol-induced liver disease depends on the amount, method of usage and duration of alcohol consumption as well as on age, gender, presence of obesity, and genetic susceptibility. Genome-wide association studies and candidate gene studies have identified genetic modifiers of ALD that can be exploited as non-invasive biomarkers, but which do not completely explain the phenotypic variability. Indeed, ALD development and progression is also modulated by epigenetic factors. The premise of this review is to discuss the role of genetic variants and epigenetic modifications, with particular attention being paid to microRNAs, as pathogenic markers, risk predictors, and therapeutic targets in ALD.

A Unifying Hypothesis Linking Hepatic Adaptations for Ethanol Metabolism to the Proinflammatory and Profibrotic Events of Alcoholic Liver Disease

The pathogenesis of alcoholic liver disease (ALD) remains poorly understood but is likely a multihit pathophysiological process. Here, we propose a hypothesis of how early mitochondrial adaptations for alcohol metabolism lead to ALD pathogenesis. Acutely, ethanol (EtOH) feeding causes a near doubling of hepatic EtOH metabolism and oxygen consumption within 2 to 3 hours. This swift increase in alcohol metabolism (SIAM) is an adaptive response to hasten metabolic elimination of both EtOH and its more toxic metabolite, acetaldehyde (AcAld). In association with SIAM, EtOH causes widespread hepatic mitochondrial depolarization (mtDepo), which stimulates oxygen consumption. In parallel, voltage-dependent anion channels (VDAC) in the mitochondrial outer membrane close. Together, VDAC closure and respiratory stimulation promote selective and more rapid oxidation of EtOH first to AcAld in the cytosol and then to nontoxic acetate in mitochondria, since membrane-permeant AcAld does not require VDAC to enter mitochondria. VDAC closure also inhibits mitochondrial fatty acid oxidation and ATP release, promoting steatosis and a decrease in cytosolic ATP. After acute EtOH, these changes revert as EtOH is eliminated with little hepatocellular cytolethality. mtDepo also stimulates mitochondrial autophagy (mitophagy). After chronic high EtOH exposure, the capacity to process depolarized mitochondria by mitophagy becomes compromised, leading to intra- and extracellular release of damaged mitochondria, mitophagosomes, and/or autolysosomes containing mitochondrial damage-associated molecular pattern (mtDAMP) molecules. mtDAMPs cause inflammasome activation and promote inflammatory and profibrogenic responses, causing hepatitis and fibrosis. We propose that persistence of mitochondrial responses to EtOH metabolism becomes a tipping point, which links initial adaptive EtOH metabolism to maladaptive changes initiating onset and progression of ALD.

Complement Factor D protects mice from ethanol-induced inflammation and liver injury

Complement plays a crucial role in microbial defense and clearance of apoptotic cells. Emerging evidence suggests complement is an important contributor to alcoholic liver disease. While complement component 1, Q subcomponent (C1q)-dependent complement activation contributes to ethanol-induced liver injury, the role of the alternative pathway in ethanol-induced injury is unknown. Activation of complement via the classical and alternative pathways was detected in alcoholic hepatitis patients. Female C57BL/6J [wild type (WT)], C1q-deficient ( C1qa-/-, lacking classical pathway activation), complement protein 4-deficient ( C4-/-, lacking classical and lectin pathway activation), complement factor D-deficient ( FD-/-, lacking alternative pathway activation), and C1qa/FD-/- (lacking classical and alternative pathway activation) mice were fed an ethanol-containing liquid diet or pair-fed control diet for 4 or 25 days. Following chronic ethanol exposure, liver injury, steatosis, and proinflammatory cytokine expression were increased in WT but not C1qa-/-, C4-/-, or C1qa/FD-/- mice. In contrast, liver injury, steatosis, and proinflammatory mediators were robustly increased in ethanol-fed FD-/- mice compared with WT mice. Complement activation, assessed by hepatic accumulation of C1q and complement protein 3 (C3) cleavage products (C3b/iC3b/C3c), was evident in livers of WT mice in response to both short-term and chronic ethanol. While C1q accumulated in ethanol-fed FD-/- mice (short term and chronic), C3 cleavage products were detected after short-term but not chronic ethanol. Consistent with impaired complement activation, chronic ethanol induced the accumulation of apoptotic cells and fibrogenic responses in the liver of FD-/- mice. These data highlight the protective role of complement factor D (FD) and suggest that FD-dependent amplification of complement is an adaptive response that promotes hepatic healing and recovery in response to chronic ethanol. NEW & NOTEWORTHY Complement, a component of the innate immune system, is an important pathophysiological contributor to ethanol-induced liver injury. We have identified a novel role for factor D, a component of the alternative pathway, in protecting the liver from ethanol-induced inflammation, accumulation of apoptotic hepatocytes, and profibrotic responses. These data indicate a dual role of complement with regard to inflammatory and protective responses and suggest that accumulation of apoptotic cells impairs hepatic healing/recovery during alcoholic liver disease.

Rosiglitazone Elicits an Adiponectin-Mediated Insulin-Sensitizing Action at the Adipose Tissue-Liver Axis in Otsuka Long-Evans Tokushima Fatty Rats

Rosiglitazone is an agonist of peroxisome proliferator-activated receptor- (PPAR-) γ that is principally associated with insulin action. The exact mechanisms underlying its insulin-sensitizing action are still not fully elucidated. It is well known that adiponectin mostly secreted in adipose tissue is an insulin sensitizer. Here, we found that treatment of Otsuka Long-Evans Tokushima Fatty (OLETF) rats with rosiglitazone (3 mg/kg, once daily, by oral gavage for 33 weeks) attenuated the increase in fasting plasma insulin concentrations and the index of the homeostasis model assessment of insulin resistance along with the age growth and glucose concentrations during an oral glucose tolerance test. In addition, the increase in plasma alanine aminotransferase activity, concentrations of fasting plasma nonesterified fatty acids and triglyceride, and hepatic triglyceride content was also suppressed. The hepatic protein expression profile revealed that rosiglitazone increased the downregulated total protein expression of insulin receptor substrate 1 (IRS-1) and IRS-2. Furthermore, the treatment suppressed the upregulated phosphorylation of IRS-1 at Ser³⁰⁷ and IRS-2 at Ser⁷³¹. The results indicate that rosiglitazone ameliorates hepatic and systemic insulin resistance, hepatic inflammation, and fatty liver. Mechanistically, rosiglitazone suppressed hepatic protein overexpression of both phosphorylated nuclear factor- (NF-) κBp65 and inhibitory-κB kinase-α/β, a transcription factor that primarily regulates chronic inflammatory responses and the upstream NF-κB signal transduction cascades which are necessary for activating NF-κB, respectively. More importantly, rosiglitazone attenuated the decreases in adipose adiponectin mRNA level, plasma adiponectin concentrations, and hepatic protein expression of adiponectin receptor-1 and receptor-2. Thus, we can draw the conclusion that rosiglitazone elicits an adiponectin-mediated insulin-sensitizing action at the adipose tissue-liver axis in obese rats. Our findings may provide new insights into the mechanisms of action of rosiglitazone.

Characterization of body composition and definition of sarcopenia in patients with alcoholic cirrhosis: A computed tomography based study

BACKGROUND

Alterations in body composition (BC) as loss of fat and muscle mass (sarcopenia) are associated with poor outcome in alcoholic cirrhosis (ALC). Prevalence of sarcopenia depends upon the method of assessment. Computed Tomography (CT) is a gold standard tool for assessing BC.

AIM

To characterize BC and define sarcopenia in ALC patients using CT.

METHODS

Single slice CT images at L3 vertebrae of healthy controls (HC) - organ transplant donors and ALC patients were analysed to give cross-sectional area of five skeletal muscles normalized for height -skeletal muscle index (SMI; cm² /m² ), area of subcutaneous (SAT;cm² ) and visceral adipose tissue (VAT;cm² ). Cut-offs for defining sarcopenia was established at 2SD below the mean of HC. HC were compared with Child A-compensated (C) and Child B+C-decompensated (DC) patients.

RESULTS

Cut-offs of SMI derived from HC (n = 275; M: 50%; age 32.2 ± 9.8 years; BMI 24.2 ± 3.2 Kg/m² ) were 36.54 in males and 30.21 in females. Sarcopenia was found in 12.8% of ALC patients [n = 148; C (31.8%): DC (68.2%); M: 100%; age 46.6 ± 9.7 years; BMI 24.5 ± 4.4]. Compared to HC, compensated patients had higher adiposity and comparable muscularity; decompensated patients had significantly lower muscle and also fat mass compared to both HC and compensated patients. HC vs C vs DC: SAT (140 ± 82 vs 177.3 ± 11 vs 112 ± 8.2); VAT (96.5 ± 6.5 vs 154.9 ± 8.7 vs 87.5 ± 6.5) and SMI (52.1 ± 0.9 vs 49.6 ± 1.2 vs 46 ± 0.9).

CONCLUSIONS

Compensated ALC have increased adiposity and relatively preserved muscularity but decompensation leads to loss of both muscle and fat mass. Prevalence of sarcopenia, based on derived ethnic cut-offs was 12.8%.

Over-expressing the soluble gp130-Fc does not ameliorate methionine and choline deficient diet-induced non alcoholic steatohepatitis in mice

Non-alcoholic steatohepatitis (NASH) is a liver disease with the potential to lead to cirrhosis and hepatocellular carcinoma. Interleukin-6 (IL-6) has been implicated in the pathogenesis of NASH, with the so-called IL-6 ‘trans-signaling’ cascade being responsible for the pro-inflammatory actions of this cytokine. We aimed to block IL-6 ‘trans-signaling’, using a transgenic mouse that overexpresses human soluble glycoprotein130 (sgp130Fc Tg mice) fed a commonly used dietary model of inducing NASH (methionine and choline deficient-diet; MCD diet) and hypothesized that markers of NASH would be ameliorated in such mice. Sgp130Fc Tg and littermate control mice were fed a MCD or control diet for 4 weeks. The MCD diet induced many hallmarks of NASH including hepatomegaly, steatosis, and liver inflammation. However, in contrast with other mouse models and, indeed, human NASH, the MCD diet model did not increase the mRNA or protein expression of IL-6. Not surprisingly, therefore, markers of MCD diet-induced NASH were unaffected by sgp130Fc transgenic expression. While the MCD diet model induces many pathophysiological markers of NASH, it does not induce increased IL-6 expression in the liver, a key hallmark of human NASH. We, therefore, caution the use of the MCD diet as a viable mouse model of NASH.

Alcoholic Liver Disease: Pathogenesis and Current Management

Excessive alcohol consumption is a global healthcare problem. The liver sustains the greatest degree of tissue injury by heavy drinking because it is the primary site of ethanol metabolism. Chronic and excessive alcohol consumption produces a wide spectrum of hepatic lesions, the most characteristic of which are steatosis, hepatitis, and fibrosis/cirrhosis. Steatosis is the earliest response to heavy drinking and is characterized by the deposition of fat in hepatocytes. Steatosis can progress to steatohepatitis, which is a more severe, inflammatory type of liver injury. This stage of liver disease can lead to the development of fibrosis, during which there is excessive deposition of extracellular matrix proteins. The fibrotic response begins with active pericellular fibrosis, which may progress to cirrhosis, characterized by excessive liver scarring, vascular alterations, and eventual liver failure. Among problem drinkers, about 35 percent develop advanced liver disease because a number of disease modifiers exacerbate, slow, or prevent alcoholic liver disease progression. There are still no FDA-approved pharmacological or nutritional therapies for treating patients with alcoholic liver disease. Cessation of drinking (i.e., abstinence) is an integral part of therapy. Liver transplantation remains the life-saving strategy for patients with end-stage alcoholic liver disease.